Suzuki ECU Diagnostics Explained

Suzuki (and Geo badged Suzuki) ECU diagnostics can be categorised into two very broad types, usually refered to as 'OBD1' and 'OBD2'. Prior to the adoption of OBD2 some countries had a mandatory requirement for On Board Diagnostics, others didn't. Most manufacturers did fit diagnostic interfaces and these were usually proprietary. The majority of Suzuki ECUs from 1991 onwards were fitted with a diagnostic link, a notable exception being the Swift GTi models.

The terms 'OBD1' and 'OBD2' are actually very specific to the US but have achieved common usage worldwide. In the US OBD2 was mandated from 1996 onwards, in Europe legislation required the adoption of OBD2 from 2001 for new petrol engined passenger vehicles through to 2004 for existing models of diesel engined passenger vehicles. Australia adopted OBD2 in 2006 and India is currently scheduled to adopt it in 2013. Of course manufacturers were free to adopt OBD2 before the mandated dates so legislation dates only mean that vehicles introduced after those dates will be OBD2, before those dates they may be OBD2 or proprietary.

The Check Engine Light Method
The most basic form of diagnostic interface fitted to a Suzuki flashes fault codes on the Check Engine Light when the interface is activated. Activating the interface requires the insertion of a jumper in the monitor coupler or the insertion of a fuse in the 'Diag' slot in the fuse box. The later method is mainly used on earlier models. The ECU flags fault codes mainly in response to gross errors, ie sensors outputs at supply voltage or grounded. The fault codes cover only emissions related performance and only current faults can be displayed.

The Check Engine Light method is covered in more detail here

The Serial Data Link (SDL)
From 1991 onwards the majority of Suzuki ECUs have a serial link that can communicate with a hand held scanner or a diagnostic interface. The Serial Data Link allows live data to be examined, current and historic fault codes to be examined and various actuators such as the EGR to be remotely operated for test purposes. From 1991 until approx. 2001 in OBD1 markets a wholely proprietary Suzuki interface was used, originally using a 12-pin ALDL type connector and then from 1996 onwards a 16-pin J1962 (OBD2) connector. It should be noted that the wiring to the ALDL connector was not the same as used by GM models; the serial link was wired to pin 9 on the J1962 connector which the specification reserves for manufacturer's assignment. The RhinoPower SDL interface is compatible with this protocol.

The SDL is covered in more detail here

SDL/KWP
From some time around 2001 Suzuki started to use a different proprietary protocol in OBD1 markets; they call this protocol SDL/KWP. As the name suggests this protocol uses a modified version of the KWP2000 protocol. The serial link is connected to pin 7 on a J1962 connector as per the OBD2 specification; an OBD2 compatible scan tool may connect to the ECU but will not receive any valid data. An ELM compatible tool can be used with a terminal emulation programme to determine the protocol used. RhinoPower is developing a scan tool that will work with this protocol.
There is more information here: pending!

Other Protocols
Some Suzukis that use an engine and electronics bought in from another supplier may use a protocol proprietary to the engine supplier. Some Suzuki models with FIAT diesel engines are known to use a FIAT version of the KWP specification.

The use of the expression 'OBD2 specification' is commonplace but it must be noted that 'OBD2' refers to a specific piece of US legislation and that there are a large number of different specifications that make up 'OBD2'. The original intention to have a common protocol was a dismal failure and the OBD2 legislation allowed several different protocols to be used with KWP2000 being added later. EOBD is to all intents and purposes the original OBD2 protocols plus KWP2000 so I will just call everything OBD2. In 2001 an international standard for on board diagnostics, ISO15031, was introduced and most markets are now adopting CANBus as the only allowed hardware protocol so some standardisation is finally happening. OBD2 Suzuki ECUs generallly use ISO9141-2 up to 2001 and KWP2000 from 2001 until the introduction of CANbus from around 2006.
Nearly all of these Suzuki ECUs also have a proprietary interface, on pin 9, for non-engine related ECUs such as airbags and ABS or use manufacturer proprietary extensions to the OBD2 protocol. To access all functions a professional scan tool is required, however for most emission related functions a generic tool such as the ELMScan will suffice. It should be noted that the ELMScan tool often fails to connect to Suzuki ECUs using KWP2000 using autoscan; manually selecting KWP2000 fast init usually succeeds.
Information on the specifics of the OBD2 protocols is widely available on many sites on the internet however the specifications are not open source nor are they cheap so there are often errors! As an OE ECU designer I do have access to most of these specifications if you have any specific queries then please ask. I am unable to provide copies of the specifications because of copyright issues. Copyright is rigidly enforced which is why you will not find these specifications on-line for free!

The Reverse Engineering pages are available through the forum and have some schematics, code disassemblies and other specific details which can be of use when fault finding at PCB level. I also have a good deal of information about the various ICs and other components that can be very difficult to find. A lot of this is not yet published so feel free to ask on the RhinoPower Forum. Please note that the forum is not there to assist with general running problems, a Factory Service Manual is the best source for that sort of information.

Key Words

ECU ECM engine management control suzuki geo vitara sidekick tracker DSM MH6211 MH6111 air temperature sensor repair caps ignition map 3d performance tuning diy efi water temperature manifold pressure software pcb map reprogram datalog o2 sensor lambda egr tbi mpi repair rhinopower